The present invention relates generally to anodes being utilized in impressed current cathodic protection system of marine submerged pipelines and structures.
Submerged metallic surfaces of pipelines and other structures in marine environment are subject to corrosion due to electrochemical reactions between the metallic surfaces and seawater they are in contact with. Cathodic protection systems are installed to limit the amount of corrosion occurring on the subjected surfaces. Impressed current cathodic protection systems are excessively used in marine environment employ a series of anodes at the sea or ocean bottom in order to mitigate and control the severity of corrosion attacks. One of the most common anode materials used in impressed current cathodic protection systems of marine structures is high silicon cast iron.
The existing impressed current cathodic protection anodes are commonly produced in the shape of simple rod or tube using sand molded casting or metal die casting techniques. Because of ocean currents and pump-jet streams from ships, especially in near piers and coast zones, the anode systems are exposed to strong forces. When submerged, the effective weight of anode system is reduced significantly in compared with onshore condition. As a result, the submerged anode system placed at the ocean or sea floor must be heavy enough to prevent any movement and subsequent failure.
Known anode systems utilize an anode sled assembly having a number of conventional cylindrical or tubular cast iron cathodic protection anodes commonly used in underground applications, attached to a frame generally made of concrete. The frame typically includes two large diameter concrete longitudinal beams connected by smaller lateral beams. The anode sled assembly includes four lifting eyes, one or two electrical cable connections for each cathodic protection anode, anode clamps to attach the cathodic protection anodes to sled, and cables to connect the anode sled to a current source. Damage to any of the cables or clamps can result in failure of the anode sled. Current output capacity and efficiency of each cathodic protection anode in a specific medium is limited by the surface area of the anode.